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Topic: Why i am killing my tip120 ? (Read 1 time) previous topic - next topic

Jan 12, 2013, 11:04 am Last Edit: Jan 12, 2013, 01:07 pm by cheesepower Reason: 1
Hi all,

I am new in electronics and encounter a problem with a tip120 transistor. I wire it this way:
http://floran.morel.free.fr/Divers/versys_bb.jpg

The problem is, the led is always ON, and when i am testing the transistor with a multimeter in diode mode, i find 0,5v between the collector and emmiter. So i kill it and i don't know why  =(

I need some help to understand where is my mistake.

SurferTim

I cannot find a datasheet on that TIP220 transistor. Can you post a link to it? Are you sure it is a TIP220 and not a TIPXXX in a TO-220 case?


My mistake, it is a TIP120 in a TO220 as you said ;)

here is a ilnk to the datasheet:
http://www.produktinfo.conrad.com/datenblaetter/150000-174999/150872-da-01-en-Transistor_TIP_120.pdf

cjdelphi

It's a Darlington, Collector, Base Emitter.


- not a mosfet as your circuit would describe.

you're not blowing them, they work still no doubt, collect D3 of Arduino to the Base Pin (middle/2 pin), Emitter to GND, Collector to your LED's GND (short lead) and the Anode + side goes straight to your 5v rail.

cjdelphi

But, add a 1 - 10k resistor on base or it could damage the arduino pin.

SurferTim

Try connecting the wire connected to the Arduino D3 pin to ground instead of the Arduino pin. Does the LED still light?

@cjdelphi: That is not what the datasheet shows. Pin 1 is the base.



you're not blowing them, they work still no doubt, collect D3 of Arduino to the Base Pin (middle/2 pin), Emitter to GND, Collector to your LED's GND (short lead) and the Anode + side goes straight to your 5v rail.


According to the datasheet, the base pin is the pin 1, right ?

SurferTim

Pin 1 is the base. Did you try the test?


#8
Jan 12, 2013, 01:30 pm Last Edit: Jan 12, 2013, 01:33 pm by cheesepower Reason: 1

Pin 1 is the base. Did you try the test?



Yes, and the led is still light

cjdelphi

ah yes sorry my bad, I looked at the Darlington first, then i went back to a similar datasheet i had open and looked, then i went back and realized.

take a look at the attachment....

cjdelphi

ah yes, my amazing circuit design skills :D

cjdelphi

#11
Jan 12, 2013, 01:38 pm Last Edit: Jan 12, 2013, 01:41 pm by cjdelphi Reason: 1
fair enough, so what resistors you using? to connect the transistor? i'd use a 1k for the base, and then 300 ohms to limit the LED current, also while you're at it, move it from 3v to 5v, it's possible if you're not
using a red led, it will be dimly lit, even less so with the voltage drop through the transistor.

Sorry but i don't understand your schematics  :smiley-eek:

cjdelphi

^^ so just swap to a 5v source and let us know the resistor values.

I put a 1K resistor between D3 and the base pin, also put a 200 ohms resistor for the led

Why do i need to change the voltage to 5v ?  3,3v is not correct ?

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